7mm RM improved

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I'm thinking about trying something with a 300 win. mag.. I want to rebarrel a 700 action with a 300 win. mag but bore it for .284". My thought here it to see if I can get better velocity with the heavier .284" bullets than what the 7mm RM will produce. I see the 300 WM is pushing 200 gr. bullets at well over 3000 fps so it shoudl work well for getting a 168 gr. and heavier .284 bullet up to 3300 - 3400 fps?

Anyone who is well versed on this type of project, please advise me. Reloading won't be an issue, I've got that worked out completely and have already started a load work up with RL25 and 168 gr. Berger's.
 
Are you referring to the 300WM cases being 2.62" long and the 7mmRM cases only being 2.5" long?

There is trade off between range and rifle weight. I like the 270 if I have to walk 4 miles. I like the 7mmRM if I am only going to walk 1 mile.
 
Look for info on the 6.5x300 weatherby. It's a little more radical than what you're looking to do, but may provide some information.
Good Luck.
 
I see the 300 WM is pushing 200 gr. bullets at well over 3000 fps
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Case capacity isn't all thats going on there.
If the .300 WinMag were a 7mm WinMag, it wouldn't do as well either.

Larger bores will push like bullet weights faster then smaller bores because there is more bullet base exposed to the pressure.

Kinda like boring out an engine to use larger pistons.
Part of the HP gain is in being able to burn more fuel. (case capacity)
But another part of the gain is the larger piston surface area for the fuel burn to push on. (bore size)

There is also the little matter of the 7mm RemMag being loaded to 61,000 PSI.
The .300 WinMag is loaded to 64,000 PSI.
(Higher compression ratio in engine speak)

I think if you took a .300 WinMag and made it a 7mm WinMag?
And loaded it to the same pressure as the 7mm RemMag?
The actual difference in performance would be so slight it would not be worth messing with.

rc
 
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it shoudl work well for getting a 168 gr. and heavier .284 bullet up to 3300 - 3400 fps?
Click to expand...

No.
Even the bigger 7mm STW on the full length magnum 2.85" case - 8mm R.M necked down - only gets a 160 up to 3075 fps (Doubletap claims 3300 which will be a good trick.)

The huge 7mm RUM fires a 160 at 3225 (Nosler) or 3275 (Doubletap.)
 
I agree with the above piston area analogy.
I own several 300 WM rifles and several 7mmRM rifles.
The 300WM converts powder into bullet energy at the muzzle more efficiently.

But 500 yards out, the 7mmRM has more power and less trajectory.
This is because there is less air resistance and drag on the smaller diameter 7mm bullet.

Next week I will be hunting over sage brush, and I will be taking 7mmRM rifles.
 
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